Contents

Welcome to Pochoir

The Pochoir Stencil Compiler

Pochoir (pronounced "PO-shwar") is a compiler and runtime system for implementing stencil computations on multicore processors. A stencil defines the value of a grid point in a d-dimensional spatial grid at time t as a function of neighboring grid points at recent times before t. A stencil computation computes the stencil for each grid point over many time steps. Using Pochoir, a user specifies a computing kernel and boundary conditions using a simple stencil language embedded in C++. The Pochoir compiler produces cache-efficient multithreaded C++ code that can be compiled with the Intel 12.0 compiler for C++ with the Cilk multithreading extensions, which is available as part of the Intel Parallel Computer suite. The Pochoir package contains two main components: a C++ template library for debugging and testing Pochoir compliance and a domain-specific compiler written in Haskell that produces highly optimized code. (Currently, the Pochoir package has only been tested on Linux systems.)

Pochoir is an open-source software project hosted by Supertech group at CSAIL, MIT. You are invited to contribute in any form (documentation, translation, writing code, fixing bugs, porting to other platforms, etc.). We are particularly interested in developing a set of real-world example stencil computations.

Performance Graphs

Comparing the number of grid points processed per second (semilogarithmic scale) for Pochoir-generated code on 12 cores versus serial- and parallel-loop implementations. In all figures, the top curve is for the Pochoir-generated code, the middle curve is for parallel loops, and the bottom curve is for serial loops. (a) A 3D wave equation with a nonperiodic boundary condition executing for 1000 time steps. (b) A 2D heat equation on a torus executing for 3200 time steps. (c) 1D pairwise sequence alignment (no time step). (d) A Lattice Boltzmann method with a nonperiodic boundary condition for 3000 time steps.